Migration behavior in minute wiring on flexible substrate and establishment of evaluation method

In order to actualize the fine pitch of wiring in FPC (Flexible Printed Circuit), the insulation degradation due to the migration becomes the problem, which cannot be ignored. Because of difference in its structure and wiring from the former printed circuit board, the analysis of migration behavior in FPC becomes important for evaluating the reliability of an electronic component based on FPC. In this research, in order to grasp the migration behavior of FPC, the paragraphed 30 mum pitch tooth profile wiring specimen was designated as the test material. Then, reliability test for evaluating the migration behavior was conducted. As a result of THB (hot high moisture bias) test, the migration occurred progressively. Various investigations were conducted for explaining about the mechanism of ionic migration. Also in this paper, the adhesive strength between the polyimide film and Cu wiring pattern and that between the polyimide film and the under-filling material was measured in order to investigate the influence of surface state of polyimide film upon the migration behavior.